Dicyanobenzene is a useful compound as a raw material of agricultural chemicals and an intermediate raw material of polyamide resins and curing agents. Dicyanobenzene can be produced by a known method involving ammoxidizing xylene (ortho-xylene, meta-xylene and para-xylene), for example, any method described in Patent Documents 1 to 5. Further, the produced dicyanobenzene may be hydrogenated by a known hydrogenation reaction so as to produce xylylenediamine, which is useful in various industrial fields such as resin curing agents, nylon, polyurethane, rubber chemicals, paper processing chemicals, and fiber treatment agents.
In hydrogenation of dicyanobenzene to produce xylylenediamine with use of a hydrogenation catalyst, it is known that use of dicyanobenzene obtained by a specific method extends the life of a hydrogenation catalyst (refer to Patent Document 6). In the specific method, first, the reaction gas in ammoxidation of xylene is contacted with an organic solvent so as to obtain a dicyanobenzene-absorbing solution comprising the organic solvent in which dicyanobenzene is dissolved. Subsequently, the dicyanobenzene-absorbing solution is contacted with a basic aqueous solution so as to cause liquid-liquid separation into an organic phase and an aqueous phase, and the aqueous phase is then removed. The organic phase is then distilled to separate compounds having a boiling point lower than that of dicyanobenzene from the organic phase, so that dicyanobenzene is obtained.